This is an example to custome youre ELF sections for initialization.
//main.c
#include <stdio.h>
#include "init.h"
static void callinit(void)
{
init_fn_t *fn;
for (fn = &__start_init_sec; fn < &__stop_init_sec; fn++)
(*fn)();
}
int main(int argc, char *argv[])
{
callinit();
return 0;
}
//a.c
#include <stdio.h>
#include "init.h"
static void a_init(void)
{
printf("a init is called.\n");
}
DECLARE_INIT(a_init);
//b.c
#include <stdio.h>
#include "init.h"
static void b_init(void)
{
printf("b init is called.\n");
}
DECLARE_INIT(b_init);
//init.h
/* Define the initialize function prototype */
typedef void (*init_fn_t)(void);
/*
* This macro is to define an function pointer which pointed the specific init function
* and located in the customize section in order to call initialize function
* together from main.
*/
#define DECLARE_INIT(func) \
static init_fn_t __fn_ ## func \
__attribute__((unused, section("init_sec"))) = func
/* These two symols are generated by ld (gcc linker). */
extern init_fn_t __start_init_sec;
extern init_fn_t __stop_init_sec;
//Makefile
CROSS:=
CC:= gcc
CFLAGS:= -Wall -c -Werror
LDFLAGS:=
OBJS:= main.o a.o b.o
OUT:= test
ifeq ($(DEBUG),1)
CFLAGS+= -g
endif
$(OUT): $(OBJS)
$(CC) $^ -o $@ $(LDFLAGS)
%*.o: %*.c
$(CC) $^ -o $@ $(CFLAGS)
.PHONY: clean
clean:
rm $(OBJS) $(OUT)
//main.c
#include <stdio.h>
#include "init.h"
static void callinit(void)
{
init_fn_t *fn;
for (fn = &__start_init_sec; fn < &__stop_init_sec; fn++)
(*fn)();
}
int main(int argc, char *argv[])
{
callinit();
return 0;
}
//a.c
#include <stdio.h>
#include "init.h"
static void a_init(void)
{
printf("a init is called.\n");
}
DECLARE_INIT(a_init);
//b.c
#include <stdio.h>
#include "init.h"
static void b_init(void)
{
printf("b init is called.\n");
}
DECLARE_INIT(b_init);
//init.h
/* Define the initialize function prototype */
typedef void (*init_fn_t)(void);
/*
* This macro is to define an function pointer which pointed the specific init function
* and located in the customize section in order to call initialize function
* together from main.
*/
#define DECLARE_INIT(func) \
static init_fn_t __fn_ ## func \
__attribute__((unused, section("init_sec"))) = func
/* These two symols are generated by ld (gcc linker). */
extern init_fn_t __start_init_sec;
extern init_fn_t __stop_init_sec;
//Makefile
CROSS:=
CC:= gcc
CFLAGS:= -Wall -c -Werror
LDFLAGS:=
OBJS:= main.o a.o b.o
OUT:= test
ifeq ($(DEBUG),1)
CFLAGS+= -g
endif
$(OUT): $(OBJS)
$(CC) $^ -o $@ $(LDFLAGS)
%*.o: %*.c
$(CC) $^ -o $@ $(CFLAGS)
.PHONY: clean
clean:
rm $(OBJS) $(OUT)